Mmmh, I didn't have such a nightmare (I guess you finally would backup /etc, /home and /usr/local and would put in an installation CD of Breezy...) but I had keyboard troubles.
I meant I wasn't able to use the arrow keys. I guess this was due to Hoary to use fr_FR@euro locale, while Breezy uses fr_FR@UTF-8. Even though I tried to configure.
Before dist-upgrading, I also ensure that ubuntu-base, ubuntu-desktop were reinstalled.
I don't understand why you have dependances issues if you don't use extra repositories...
Try to deinstall the Yahoo messenger package before you dist-upgrade. This package, since it's a Debian and not Ubuntu one, can be the cause of your trouble.
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By the way, I have this line in my sources.list among others :